Free Foundation's Edge by Isaac Asimov

I am forced by the responsibilities of my position to consider the possibility. Let me ask you again if you have any indication as to where he might think the Second Foundation exists, and where he might go.”
    “I have none.”
    “He has never given you any hints in that direction?”
    “No, of course not.”
    “Never? Don’t dismiss the thought easily. Think! Never?”
    “Never,” said Compor firmly.
    “No hints? No joking remarks? No doodles? No thoughtful abstractions at moments that achieve significance as you look back on them?”
    “None. I tell you, Madam Mayor, his dreams of the Second Foundation are the most nebulous starshine. You know it, and you but waste your time and your emotions in your concern over it.”
    “You are not by some chance suddenly changing sides again and protecting the friend you delivered into my hands?”
    “No,” said Compor. “I turned him over to you for what seemed to me to be good and patriotic reasons. I have no reason to regret the action, or to change my attitude.”
    “Then you can give me no hint as to where he might go once he has a ship at his disposal?”
    “As I have already said-“
    “And yet, Councilman,” and here the lines of the Mayor’s face so folded as to make her seem wistful, “I would like to know where he goes.”
    “In that case, I think you ought to place a hyper-relay on his ship.”
    “I have thought of that, Councilman. He is, however, a suspicious man and I suspect he will find it-however cleverly it might be placed. Of course, it might be placed in such a way that he cannot remove it without crippling the ship, and he might therefore be forced to leave it in place-“
    “An excellent notion.”
    “Except that,” said Branno, “he would then be inhibited. He might not go where he would go if he felt himself free and untrammeled. The knowledge I would gain would be useless to me.”
    “In that case, it appears you cannot find out where he will go.”
    “I might, for I intend to be very primitive. A person who expects the completely sophisticated and who guards against it is quite apt never to think of the primitive. -I’m thinking of having Trevize followed.”
    “Followed?”
    “Exactly. By, another pilot in another spaceship. See how astonished you are at the thought? He would be equally astonished. He might not think of scouring space for an accompanying mass and, in any case, we will see to it that his ship is not equipped with our latest mass-detection devices.”
    Compor said, “Madam Mayor, I speak with all possible respect, but I must point out that you lack experience in space flight. To have one ship followed by another is never done-because it won’t work. Trevize will escape with the first hyperspatial jump. Even if he doesn’t know he is being followed, that first jump will be his path to freedom. If he doesn’t have a hyper-relay on board ship, he can’t be traced.”
    “I admit my lack of experience. Unlike you and Trevize, I have had no naval training. Nevertheless, I am told by my advisers-who have had such training-that if a ship is observed immediately prior to a jump, its direction, speed, and acceleration make it possible to guess what the jump might be-in a general way. Given a good computer and an excellent sense of judgment, a follower might duplicate the jump closely enough to pick up the trail at the other end -especially if the follower has a good mass-detector.”
    “That might happen once,” said Compor energetically, “even twice if the follower is very lucky, but that’s it. You can’t rely on such things.”
    “Perhaps we can. -Councilman Compor, you have hyper-raced in your time. You see, I know a great deal about you. You are an excellent pilot and have done amazing things when it comes to following a competitor through a jump.”
    Compor’s eyes widened. He almost squirmed in his chair. “I was in college then. I am older now.”
    “Not too old. Not yet thirty-five. Consequently you